/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.SortedLists.KeyAbsentBehavior;
import com.google.common.collect.SortedLists.KeyPresentBehavior;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import javax.annotation.Nullable;

/**
 * A {@link RangeMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * @author Louis Wasserman
 * @since 14.0
 */
@Beta
@GwtIncompatible // NavigableMap
public class ImmutableRangeMap<K extends Comparable<?>, V> implements RangeMap<K, V>, Serializable {

    private static final ImmutableRangeMap<Comparable<?>, Object> EMPTY =
            new ImmutableRangeMap<Comparable<?>, Object>(ImmutableList.<Range<Comparable<?>>>of(), ImmutableList.of());

    /**
     * Returns an empty immutable range map.
     */
    @SuppressWarnings("unchecked")
    public static <K extends Comparable<?>, V> ImmutableRangeMap<K, V> of() {
        return (ImmutableRangeMap<K, V>) EMPTY;
    }

    /**
     * Returns an immutable range map mapping a single range to a single value.
     */
    public static <K extends Comparable<?>, V> ImmutableRangeMap<K, V> of(Range<K> range, V value) {
        return new ImmutableRangeMap<K, V>(ImmutableList.of(range), ImmutableList.of(value));
    }

    @SuppressWarnings("unchecked")
    public static <K extends Comparable<?>, V> ImmutableRangeMap<K, V> copyOf(RangeMap<K, ? extends V> rangeMap) {
        if (rangeMap instanceof ImmutableRangeMap) {
            return (ImmutableRangeMap<K, V>) rangeMap;
        }
        Map<Range<K>, ? extends V> map = rangeMap.asMapOfRanges();
        ImmutableList.Builder<Range<K>> rangesBuilder = new ImmutableList.Builder<Range<K>>(map.size());
        ImmutableList.Builder<V> valuesBuilder = new ImmutableList.Builder<V>(map.size());
        for (Entry<Range<K>, ? extends V> entry : map.entrySet()) {
            rangesBuilder.add(entry.getKey());
            valuesBuilder.add(entry.getValue());
        }
        return new ImmutableRangeMap<K, V>(rangesBuilder.build(), valuesBuilder.build());
    }

    /**
     * Returns a new builder for an immutable range map.
     */
    public static <K extends Comparable<?>, V> Builder<K, V> builder() {
        return new Builder<K, V>();
    }

    /**
     * A builder for immutable range maps. Overlapping ranges are prohibited.
     */
    public static final class Builder<K extends Comparable<?>, V> {
        private final List<Map.Entry<Range<K>, V>> entries;

        public Builder() {
            this.entries = Lists.newArrayList();
        }

        /**
         * Associates the specified range with the specified value.
         *
         * @throws IllegalArgumentException if {@code range} is empty
         */
        @CanIgnoreReturnValue
        public Builder<K, V> put(Range<K> range, V value) {
            checkNotNull(range);
            checkNotNull(value);
            checkArgument(!range.isEmpty(), "Range must not be empty, but was %s", range);
            entries.add(Maps.immutableEntry(range, value));
            return this;
        }

        /**
         * Copies all associations from the specified range map into this builder.
         */
        @CanIgnoreReturnValue
        public Builder<K, V> putAll(RangeMap<K, ? extends V> rangeMap) {
            for (Entry<Range<K>, ? extends V> entry : rangeMap.asMapOfRanges().entrySet()) {
                put(entry.getKey(), entry.getValue());
            }
            return this;
        }

        /**
         * Returns an {@code ImmutableRangeMap} containing the associations previously added to this
         * builder.
         *
         * @throws IllegalArgumentException if any two ranges inserted into this builder overlap
         */
        public ImmutableRangeMap<K, V> build() {
            Collections.sort(entries, Range.RANGE_LEX_ORDERING.onKeys());
            ImmutableList.Builder<Range<K>> rangesBuilder = new ImmutableList.Builder<Range<K>>(entries.size());
            ImmutableList.Builder<V> valuesBuilder = new ImmutableList.Builder<V>(entries.size());
            for (int i = 0; i < entries.size(); i++) {
                Range<K> range = entries.get(i).getKey();
                if (i > 0) {
                    Range<K> prevRange = entries.get(i - 1).getKey();
                    if (range.isConnected(prevRange) && !range.intersection(prevRange).isEmpty()) {
                        throw new IllegalArgumentException(
                                "Overlapping ranges: range " + prevRange + " overlaps with entry " + range);
                    }
                }
                rangesBuilder.add(range);
                valuesBuilder.add(entries.get(i).getValue());
            }
            return new ImmutableRangeMap<K, V>(rangesBuilder.build(), valuesBuilder.build());
        }
    }

    private final transient ImmutableList<Range<K>> ranges;
    private final transient ImmutableList<V> values;

    ImmutableRangeMap(ImmutableList<Range<K>> ranges, ImmutableList<V> values) {
        this.ranges = ranges;
        this.values = values;
    }

    @Override
    @Nullable
    public V get(K key) {
        int index = SortedLists.binarySearch(ranges, Range.<K>lowerBoundFn(), Cut.belowValue(key),
                KeyPresentBehavior.ANY_PRESENT, KeyAbsentBehavior.NEXT_LOWER);
        if (index == -1) {
            return null;
        } else {
            Range<K> range = ranges.get(index);
            return range.contains(key) ? values.get(index) : null;
        }
    }

    @Override
    @Nullable
    public Map.Entry<Range<K>, V> getEntry(K key) {
        int index = SortedLists.binarySearch(ranges, Range.<K>lowerBoundFn(), Cut.belowValue(key),
                KeyPresentBehavior.ANY_PRESENT, KeyAbsentBehavior.NEXT_LOWER);
        if (index == -1) {
            return null;
        } else {
            Range<K> range = ranges.get(index);
            return range.contains(key) ? Maps.immutableEntry(range, values.get(index)) : null;
        }
    }

    @Override
    public Range<K> span() {
        if (ranges.isEmpty()) {
            throw new NoSuchElementException();
        }
        Range<K> firstRange = ranges.get(0);
        Range<K> lastRange = ranges.get(ranges.size() - 1);
        return Range.create(firstRange.lowerBound, lastRange.upperBound);
    }

    /**
     * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    public void put(Range<K> range, V value) {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    public void putCoalescing(Range<K> range, V value) {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    public void putAll(RangeMap<K, V> rangeMap) {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    public void clear() {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    public void remove(Range<K> range) {
        throw new UnsupportedOperationException();
    }

    @Override
    public ImmutableMap<Range<K>, V> asMapOfRanges() {
        if (ranges.isEmpty()) {
            return ImmutableMap.of();
        }
        RegularImmutableSortedSet<Range<K>> rangeSet =
                new RegularImmutableSortedSet<Range<K>>(ranges, Range.RANGE_LEX_ORDERING);
        return new ImmutableSortedMap<Range<K>, V>(rangeSet, values);
    }

    @Override
    public ImmutableMap<Range<K>, V> asDescendingMapOfRanges() {
        if (ranges.isEmpty()) {
            return ImmutableMap.of();
        }
        RegularImmutableSortedSet<Range<K>> rangeSet =
                new RegularImmutableSortedSet<Range<K>>(ranges.reverse(), Range.RANGE_LEX_ORDERING.reverse());
        return new ImmutableSortedMap<Range<K>, V>(rangeSet, values.reverse());
    }

    @Override
    public ImmutableRangeMap<K, V> subRangeMap(final Range<K> range) {
        if (checkNotNull(range).isEmpty()) {
            return ImmutableRangeMap.of();
        } else if (ranges.isEmpty() || range.encloses(span())) {
            return this;
        }
        int lowerIndex = SortedLists.binarySearch(ranges, Range.<K>upperBoundFn(), range.lowerBound,
                KeyPresentBehavior.FIRST_AFTER, KeyAbsentBehavior.NEXT_HIGHER);
        int upperIndex = SortedLists.binarySearch(ranges, Range.<K>lowerBoundFn(), range.upperBound,
                KeyPresentBehavior.ANY_PRESENT, KeyAbsentBehavior.NEXT_HIGHER);
        if (lowerIndex >= upperIndex) {
            return ImmutableRangeMap.of();
        }
        final int off = lowerIndex;
        final int len = upperIndex - lowerIndex;
        ImmutableList<Range<K>> subRanges = new ImmutableList<Range<K>>() {
            @Override
            public int size() {
                return len;
            }

            @Override
            public Range<K> get(int index) {
                checkElementIndex(index, len);
                if (index == 0 || index == len - 1) {
                    return ranges.get(index + off).intersection(range);
                } else {
                    return ranges.get(index + off);
                }
            }

            @Override
            boolean isPartialView() {
                return true;
            }
        };
        final ImmutableRangeMap<K, V> outer = this;
        return new ImmutableRangeMap<K, V>(subRanges, values.subList(lowerIndex, upperIndex)) {
            @Override
            public ImmutableRangeMap<K, V> subRangeMap(Range<K> subRange) {
                if (range.isConnected(subRange)) {
                    return outer.subRangeMap(subRange.intersection(range));
                } else {
                    return ImmutableRangeMap.of();
                }
            }
        };
    }

    @Override
    public int hashCode() {
        return asMapOfRanges().hashCode();
    }

    @Override
    public boolean equals(@Nullable Object o) {
        if (o instanceof RangeMap) {
            RangeMap<?, ?> rangeMap = (RangeMap<?, ?>) o;
            return asMapOfRanges().equals(rangeMap.asMapOfRanges());
        }
        return false;
    }

    @Override
    public String toString() {
        return asMapOfRanges().toString();
    }

    /**
     * This class is used to serialize ImmutableRangeMap instances. Serializes the
     * {@link #asMapOfRanges()} form.
     */
    private static class SerializedForm<K extends Comparable<?>, V> implements Serializable {

        private final ImmutableMap<Range<K>, V> mapOfRanges;

        SerializedForm(ImmutableMap<Range<K>, V> mapOfRanges) {
            this.mapOfRanges = mapOfRanges;
        }

        Object readResolve() {
            if (mapOfRanges.isEmpty()) {
                return of();
            } else {
                return createRangeMap();
            }
        }

        Object createRangeMap() {
            Builder<K, V> builder = new Builder<K, V>();
            for (Entry<Range<K>, V> entry : mapOfRanges.entrySet()) {
                builder.put(entry.getKey(), entry.getValue());
            }
            return builder.build();
        }

        private static final long serialVersionUID = 0;
    }

    Object writeReplace() {
        return new SerializedForm<K, V>(asMapOfRanges());
    }

    private static final long serialVersionUID = 0;
}
